The present technology relates to a technical field of a zoom lens and an imaging apparatus of a five-group configuration having positive, negative, positive, negative and positive refractive powers in order from an object side to an image side.
In recent years, with the spread of imaging apparatuses such as digital cameras, there has been a demand for a bright open f-number, fast auto-focusing speed, high short-range performance and the like, as well as high image quality, compactness, and a high zoom ratio, and thus a demand for the imaging apparatus is diversified.
In general, there is an optical system of a positive lead as an optical system of a zoom lens satisfying a high zoom ratio. Since a variation in the open f-number from a wide-angle end to a telephoto end can be relatively smaller in the optical system of a positive lead as compared with an optical system of a negative lead and a high zoom ratio can be achieved, it is possible to secure the bright open f-number in an entire zoom range.
As the optical system of a positive lead of the five-group configuration having positive, negative, positive, negative and positive refractive power, for example, there are configurations disclosed in Japanese Unexamined Patent Application Publication No. 2010-14866 and Japanese Unexamined Patent Application Publication No. 2009-282429.
In the configurations disclosed in Japanese Unexamined Patent Application Publication No. 2010-14866 and Japanese Unexamined Patent Application Publication No. 2009-282429, since the size of a first lens group is reduced by an action of negative refractive power of a fourth lens group and zooming is performed by a relatively large number of groups termed the five-group configuration, there is an advantage of easily securing high optical performance in an entire zoom area even when an aperture ratio is enlarged.